1. Field of the Invention
This invention relates to thickeners based on an aqueous preparation of nonionic, water-dispersible or water-soluble polyurethanes, to their production and to their use.
2. Discussion of Related Art
Associative polyurethane-based thickeners are linear or branched nonionic polymers with hydrophilic and hydrophobic segments. They are being increasingly used as a substitute for or in addition to the cellulose ethers traditionally used as thickeners in paints and lacquers and also the alkali-soluble polyacrylates. Polyurethane thickeners have the following advantages over these traditional thickeners:
lower viscosity on incorporation PA1 less tendency to splash during spread coating PA1 better color characteristics PA1 higher gloss through less flocculation PA1 lower sensitivity of the coatings to water PA1 less vulnerability to microbial attack PA1 low intrinsic viscosity in the made-up form and, hence, good dosability PA1 a good thickening effect in the dispersions to be thickened PA1 a minimal reduction in the viscosity of the thickened dispersions under shear, substantially newtonian flow behavior. PA1 (a) at least one water-soluble polyether polyol PA1 (b) at least one water-insoluble organic polyisocyanate PA1 (c) at least one monofunctional hydrophobic organic compound selected from compounds containing an isocyanate-reactive hydrogen atom and organic monoisocyanates and PA1 (d) at least one polyhydric alcohol or polyhydric ether alcohol. PA1 (a) polyfunctional isocyanates with PA1 (b) polyether polyols, PA1 (c) monohydric alcohols and PA1 (d) if desired, polyhydric alcohols, PA1 R.sup.2 is the residue of the monohydric alcohol (c) reacted with isocyanate PA1 R.sup.3 is the residue of the diisocyanate reacted with isocyanate-reactive OH groups PA1 n=20 to 400 and PA1 m=1 to 10, preferably 1 to 5 (the best results being obtained where m=1 or 2).
Polyurethane thickeners of the type in question belong to the prior art. Their composition, production and use are described, for example, in U.S. Pat. No. 4,155,892. According to this document, the polyurethanes are produced by reaction of the following components:
U.S. Pat. No. 4,079,028 relates to similar subject matter.